Substrate intended to act as a cultivation support and use for the preparation in particular of sport surfaces

ABSTRACT

A culture support substrate comprising: a first part, making up the backbone of the substrate and representing more than 70% of the total volume of the substrate, composed of particles P &gt;100 μm  with particle size greater than 100 μm, the particles as a whole consisting of hard particles P H&gt;100  and/or of resilient particles P R&gt;100 , wherein the resilient particles make up a proportion by volume PV of between 0% and 100% by volume of this first part; a second part of corpuscular components P &lt;100  with a particle size of less than 100 μm, and making up from 0 to 450 g/l of the substrate; a third part, making up from 0 to 200 g/l of the substrate, composed of fine fibres between 3 mm and 100 mm in length and between 5 μm and 35 μm in diameter; and a fourth part, making up from 0 to 200 g/l of the substrate.

The present invention relates to a substrate intended for use as aculture medium, in particular for natural turf, in particular to achievea natural grass sports surface intended for the sports of football,rugby, or equestrian sports such as flat racing or trotting, polo, showjumping and dressage, for example.

The surface traditionally used for these numerous sports is grass, moreprecisely natural turf: this is recognised as the ideal surface in thesummer, but has the disadvantage of being sensitive to climaticconditions and of not being able to withstand intensive use withoutdeterioration when conditions are unfavourable, especially in case ofprecipitation or frost.

In order to remedy this disadvantage, one idea was to replace naturalturf by artificial surfaces, and in particular synthetic turf forfootball or rugby and, for horse tracks, arenas and race courses, bysynthetic surfaces based on sand, in particular silica sand, possiblycombined with elements such as mesh, fibres, ash, ground syntheticelements, paraffin and any conceivable elements to increase the cohesionof the track or reduce its vulnerability to frost and its need forwatering.

However, these surfaces present major disadvantages compared withnatural turf surfaces, both ecologically and from the economic point ofview, in terms of ease of use, the amenity of players and of theneighbourhood and the safety of play.

Indeed, natural turf, like all other plants, contributes to theenvironment by means of photosynthesis, acting as a veritablesolar-powered air conditioner, by keeping the temperature of the groundat around 20° C. while the temperature of synthetic surfaces reaches 60°C. in the sun, and finally it contributes to the purification of air andwater by absorbing fine dust; conversely, synthetic surfaces do not trapdirt or dust but produce them, releasing the resulting products into theenvironment, and they smell bad in summer and pose a recycling problem.Again, in economic terms, the price of a sports surface made of turf, interms of life cycle cost, is advantageous due to the fact that theinvestment is less and it lasts longer than synthetic surfaces, whichhave to be changed after 10 years. Another huge advantage of turfcompared with synthetic surfaces is the amenity and safety of players:first of all, turf allows the ground to be rendered firm enough to besupportive and restitute energy and thus spare the muscles of theathletes and, secondly, allows the ground to remain sufficiently flatand springy and at the same time resilient enough to dampen running andspare the joints of the athletes. So turf spares the muscles of athletesand/or animals.

Despite their disadvantages as described above in comparison withnatural turf in ideal conditions, substitute surfaces for natural turfare becoming more widespread, to the detriment of the latter, with“synthetic turf” for football pitches, sand and fibres or textiles orground-up materials for racecourses and arenas: in fact, natural turfpresents the material disadvantage of not being in the right conditionin all circumstances. This disadvantage is now regarded as anunacceptable handicap and outweighs all other advantages (economic,ecological and health) of natural turf in comparison with artificialsurfaces.

To remedy the disadvantages of the lack of stability of turf in dampperiods, it has already been proposed that numerous elements be added tosubstrates for growing turf and in particular meshes of plastic fibres,then coarse synthetic fibres and finally, last of all, “fine” syntheticfibres.

Just as concrete has been strengthened and reinforced by wide-mesh metalmeshes (reinforced concrete) then by the addition of relatively finesynthetic fibres (with a diameter greater than or equal to 100 μm), thenby fibres known as microfibres (with a diameter greater than or equal to50 μm), in the same way, it has been proposed that fibres be added tosubstrates for growing grass, with strips made from polypropylenethreads (such as those marketed under the registered trade mark Netlon)then by the addition of finer and finer fibres, precisely thoseavailable on the market because they are used to reinforce concrete.

Furthermore, in order to improve the resistance of a turf substituteessentially constituted of sand, it has already been proposed toincorporate fibres finer than those used in concrete. For example, it isknown (document FR-2.707.03-A) that an artificial sports surface can beobtained without turf, resistant to shearing, with the aid of amechanism similar to that of the resistance given to the ground by theroots of turf, by incorporating a dose by weight of 1 to 5% of fibres offine section (5 to 20 μm) and of relatively short length (4 to 75 mm) ina substrate which is essentially sandy, having a granulometry of between10 μm and 20 mm with a dose of between 1 and 5% dosage by weight.

These additions are more and more effective in “reinforcing” asubstitute surface, in the same way as concrete: in fact, what isobtained is a surface which attains good performances in terms ofresistance to shearing, but, unfortunately, this improvement inresistance is attained at the expense of flexibility.

In order to remedy the disadvantage of a frost-susceptible soil and alsoto bring greater flexibility to the surface made of turf, it hasrecently been proposed to add granules of cork and more particularlybaked cork with coarse granulometry (>3 mm), medium granulometry (500 μmto 3 mm) and fine granulometry (<500 μm) in order to give improvedcharacteristics of frost resistance to a culture substrate into which itis incorporated, as a result of the dual effect of the insulatingcharacter of the cork and of its resilience, which enables it to “damin” the increased volume of water under the effect of freezing and underthe effect of permeability conferred by the coarse particles of cork. Atthe same time, cork presents the benefit of giving the substratelightness, flexibility and resistance to compaction by its density andits resilient character. Moreover, if the large grains improve thepermeability of the substrate, the small grains of cork, which are alsonon-swelling, offer a great capillary water-retention capacity due tothe high surface tension of the cork and of the ratio between surfaceand volume.

However, although the incorporation of cork enables an improvement inflexibility and good behaviour in case of frost, especially when coarseparticles are added, this is done to the detriment of the substrate'scohesion and resistance to shearing, especially when coarse particlesare added.

Another objective of this invention is to provide a substrate intendedfor use in growing, especially of natural turf, which enables a sportssurface to be produced, especially of natural turf, which is acceptablefor any type of sport.

Another objective of this invention is to provide such a substrate whichis highly resistant, very flexible, with good drainage, frost-resistantand not affected by very heavy precipitation.

These objectives, together with others which will become apparentfurther on, are attained by a substrate intended for use as a culturemedium, which is characterised, according to this invention, by the factthat it comprises:

a first part, constituting the skeleton of the substrate andrepresenting more than 70% of the total volume of the substrate,composed of particles P_(>100) with a granulometry greater than 100 μm,all of these particles being constituted by hard particles P_(D>100)and/or resilient particles P_(R>100) said resilient particles P_(R>100)constituting a proportion by volume PV of between 0% and 100% by volumeof this first part;

a second part of particulate elements P_(<100) smaller than 100 μm, thispart constituting from 0 to 450 grams per litre of said substrate;

a third part, constituting from 0 to 200 grams per litre of saidsubstrate, composed of fine fibres of a length between 3 mm and 100 mmand a diameter of between 5 μm and 35 μm;

a fourth part, constituting from 0 to 200 grams per litre of saidsubstrate, composed of other elongated and/or surface inclusions, eachof these elongated or surface inclusions having at least one of theirdimensions a great deal larger than the granulometry of the particles ofthe first part, and the sum of the doses of the third part and of thefourth part being more than 0.5 grams per litre of said substrate.

Preferably, all of the particles of a dimension of over 180 μm or lessthan 100 μm represent less than 1000 grams per litre of substrate.

According to a first embodiment of this invention, for a proportion byvolume PV of resilient particles P_(R>100) of less than 5%, the sum ofthe dosage D_(F) of the fine fibres and of the dosage D_(Al) of all theother inclusions of the fourth part is more than 0.5 g/litre ofsubstrate and 20 g/litre of substrate.

According to a second embodiment of this invention, for a proportion byvolume PV of resilient particles P_(R>100) of over 5% the sum of thedosage D_(F) of fine fibres and of the dosage D_(Al) of all the otherinclusions of the fourth part is greater than 1 g/litre of substrate.

According to a third embodiment of this invention, for a proportion byvolume PV of resilient particles P_(>100) of between 5% and 60%, thedosage D_(F) of fine fibres is greater than 1 g/litre of substrate, andthe sum of the dosage D_(F) of fine fibres and of the dosage D_(Al) ofall the other inclusions of the fourth part is less than 80 g/litre ofsubstrate.

According to a fourth embodiment of this invention, for a proportion byvolume PV of resilient particles P_(R>100) greater than 60%, the sum ofthe dosage D_(F) of the fine fibres and of the dosage D_(Al) of all theother inclusions of the fourth part is between 7 g/litre of substrateand 40 g/litre of substrate.

According to a fifth embodiment of this invention, for a proportion byvolume PV of resilient particles P_(R>100) of less than 60%, the sum ofthe dosage D_(F) of the fine fibres and of the dosage D_(Al) of all theother inclusions of the fourth part is between 2 g/litre of substrateand 80 g/litre of substrate

According to a sixth embodiment of this invention, for a proportion byvolume PV of resilient particles P_(R>100) greater than 60%, the sum ofthe dosage D_(F) of the fine fibres and of the dosage D_(Al) of all theother inclusions of the fourth part is between 5 g/litre of substrateand 200 g/litre of substrate.

Advantageously, the hard particles of the first part are grains ofsilica sand.

Preferably, the resilient particles PR of the first part are grains ofcork.

Advantageously, the particulate elements of the second part areconstituted of clay, of loam, of sand whose granulometry is less than100 μm, of organic matter, of fine porous elements such as zeolitepowder, coral or of diatomaceous earth.

Preferably, the particulate elements of the second part having adimension of less than 20 μm represent less than 60 g/l of substrate andthe particulate elements having a dimension of less than 100 μmrepresent less than 300 g/l of substrate.

According to one variant embodiment, the particulate elements of thesecond part having a dimension of less than 80 μm represent less than 45g/l of substrate. Advantageously, the fine fibres of the third part arehollow polyester fibres with a diameter of between 10 μm and 20 μm.

Preferably, at least 20% of the fibres of the third part are encased ina water-repellent lubricant product, such as for example silicone.

Advantageously, more than 50% of the weight of the fine fibres of thethird part is constituted by fine fibres whose diameter is less than 10%of the mean granulometry of the hard particles of this substrate.

Preferably, the proportion by volume PV of the resilient particlesP_(R>100) in the substrate is more than 5% and less than 60%, and morethan 50% of the weight of the fine fibres of the third part isconstituted by fine fibres with a diameter of less than 10% of the meangranulometry of the hard particles.

When the hard particles are grains of sand, firstly, more than 80% byweight of these grains have a granulometry of between 200 μm and 400 μm,and, secondly, the fine fibres of the third part are hollow polyesterfibres, with a diameter of between 12 and 30 μm and siliconised on thesurface.

A substrate according to this invention enables the realisation,optionally in situ, of sports surfaces, of terraced surfaces, of amedium for the transplantation of vegetables or for growing turf instrips.

According to a preferred embodiment, the sports surface is constitutedby juxtaposed cells, bounded by walls, and filled with substrate to aheight at least equal to that of these walls.

The following description, which is by no means limitative, will enablea person skilled in the art to understand better not only the advantagesof this invention, but also its implementation and its applications.

A substrate according to this invention intended for use as culturemedium, in particular for turf, comprises:

a first part, constituting the skeleton of the substrate andrepresenting more than 70% of the total volume of the substrate,composed of particles P_(>100) with a granulometry of more than 100 μm,all of these particles being constituted of hard particles P_(D>100)and/or resilient particles P_(R>100) these resilient particles P_(R>100)constituting a proportion by volume PV of between 0% and 100% by volumeof this first part;

a second part of particulate elements P_(>100) smaller than 100 μm, thispart constituting 0 to 450 grams per litre of the substrate;

a third part, constituting from 0 to 200 grams per litre of thesubstrate, composed of fine fibres with a length between 3 mm and 100 mmand a diameter of between 5 μm and 35 μm;

a fourth part, constituting from 0 to 200 grams per litre of thesubstrate, composed of other elongated and/or surface inclusions, eachof these elongated or surface inclusions having at least one of theirdimensions a great deal larger than the granulometry of the particles ofthe first part, and the sum of the doses of the third part and of thefourth part being more than 3 grams per litre of the substrate.

It should be pointed out here that this invention must make it possibleto meet the following various conditions:

the substrate must have a poral volume as large as possible of pores oflarge dimension corresponding to free water, which is achieved by meansof particles of large size but at the same time with a reserve of usablewater which is as large as possible, which is achieved by means ofelements of small size and high surface tension;

fibres available in sufficient quantity and at a price compatible withthe application;

fibres which satisfy the requirements of the principle of precaution interms of risk to health in case of inhalation of micro-fibres;

fibres which contribute, if necessary, to increasing the reserve ofcapillary water available for the sprouting then the growth of the turfor plants cultivated in the substrate.

It has been shown, in surprising fashion, that it is possible to obtaina soil compatible with the culture of the turf, which is relativelysatisfactory in terms of cleanliness and very satisfactory for a soil inwhich the level of particles with a granulometry of less than 20 μm isless than 60 grams/litre of substrate and in which the level ofparticles with a granulometry of less than 100 μm is less than 300grams/litre of substrate: the surface thus obtained is relativelypermeable.

According to another embodiment of the invention, the particulateelements of the second part are selected to have a dimension of lessthan 80 μm, representing less than 45 g/l of substrate: the surface thusobtained is highly permeable.

To respect the principle of precaution, and so as not to present anyrisk to the health of persons who have to handle them in order toproduce the substrate and throughout the life cycle of the substrate, itis known that a diameter of micro-fibre of over 3 microns is consideredto be the maximum diameter which can be inhaled, and that a diameter of6 microns is the diameter above which the current legislation does notclass fibres as a function of a potential risk to health: it wasconsidered preferable to use a diameter of 10 microns in order to retaina large safety margin. Consideration has been given, not only to thedimension of the fibres which are incorporated, but also to what happensto them over time and how they may or may not decompose into finerfibrils. In this respect, known fibres, made of polyester, cannotdecompose into smaller fibres due to their method of fabrication and arerecognised as harmless to the environment and to health: they allow theprinciple of precaution to be respected.

Polyester fibres with a diameter of more than 10 μm are compatible withthese safety measures and are currently available on the market. Aprudent minimum diameter of 10 μm corresponds to a hollow polyesterfibre with a titre of 1.15 dtex and a minimum diameter of 6 μmcorresponds to a titre of 0.4 dtex.

There are two possibilities envisaged to allow a fibre to move beforebecoming taut in a poral network during a shearing movement:

either the grains are in rigid sand, in which case it is necessary forthe cross-sectional diameter of the fibre to be smaller than thediameter of the hole between three contiguous grains in the plane formedby the centre of these three grains (like the thread which passesthrough the eye of a needle): if a fibre has a diameter of more than ⅕of the diameter of three contiguous grains, these grains must move asidein order to allow the fibre to pass without crushing it and so there isno degree of freedom for the fibre in these conditions;

or the grains between which the fibre coils up are resilient grains andin particular if these are grains of cork: the condition of thedimension of the fibre in relation to the dimension of the grain of corkis not necessary insofar as the fibre, by resting on the resilientgrain, will crush the latter without opposing the shearing movement andthe whole will resume its position after the strain.

However, since the granulometry of the substrates according to theinvention is not homometric and since a fibre, which is very long inrelation to the dimension of a grain of sand, passes through a greatmany pores on its path and since the diameter of the fibre must allow itto avoid being “caught” too often on its path, there has to be a largedifference in diameter between the passage delimited by three grains andthe diameter of a fibre (to clarify, a fibre 3 cm long corresponds to100 times the dimension of a grain of sand of 300 μm). This depends notonly on the diameter of the fibre, but also on its flexibility (whichincreases when the diameter diminishes) and its lubrication and ofcourse on the statistical distribution of the dimensions of the passagesin the porous volume as a function of the granulometric distribution ofthe sand; while it may be easy to give a diameter in a homometric mediumbeyond which it is known that the fibre is jammed, it is not easy todetermine theoretically a diameter below which the fibre will slide inthe porous volume before becoming taut and blocking any movement.

Tests which have been conducted have shown that, surprisingly, it ispossible to obtain a satisfactory macroscopic effect when at least 50%of the fibres have a diameter of less than D50/10, and very satisfactoryfor a diameter of under D50/20, D50 being the maximum grain diameter of50% of the grains of sand of the substrate, i.e. all the hard particleswith a dimension of under D50 represent half the weight of all the hardparticles: in other words, more than 50% of the weight of the finefibres of the third part is constituted by fine fibres whose diameter isless than 10% of the mean granulometry of the hard particles. Thiscondition is particularly advantageous when the proportion by volume PVof the resilient particles P_(R>100) in the substrate is more than 5%and less than 60%.

For the aspect of flexibility and for the effectiveness of blocking ofthe fibre, it is preferable to have a diameter as small as possible; butthe longer the fibre, the harder it is to retain flexibility, and theeasier it is to engage the substrate, the harder it is to incorporatethe fibre into the substrate.

Noticeable effectiveness commences at a length of fibre of 5mm but it ispreferable to have a length of more than 20 mm and the results improvewhen the length of fibre increases. A fibre of 60 mm is very effectiveand it would be desirable to have lengths of fibres of up to 100 or 200mm or perhaps even more, but in recently-conducted tests there has beenno success in incorporating them, because it becomes harder and harderto incorporate fibres as length increases.

Other tests have shown, surprisingly, that a satisfactory macroscopiceffect can be obtained for a fibre of a diameter of less than D30/10 andvery satisfactory for a diameter of less than D30/20, D30 being themaximum diameter of grain of 30% by weight of the hard grains of thesubstrate.

Preferably, a small diameter of fibre is better in order to obtain bothbetter blocking and greater flexibility; but it has been found that thesmaller the diameter, the harder it is to separate the fibres from eachother and to mix them in the substrate, which causes the effectivenessof the fibres to be reduced.

Taking these factors into account, experience shows that a satisfactoryresult is obtained in a sand with a granulometry of between 200 μm and1000 μm for a hollow polyester fibre of a diameter between 12 and 30 μm,corresponding to a titre of between 1.6 dtex and 34 dtex.

Siliconised fibres have the advantage of “sliding” better in the porousvolume of the sand with the aid of a “sleeve” of droplets resulting fromthe water-repelling property induced by the coating of silicone: this isa positive effect for the flexibility of the substrate for a givendiameter of fibre. Conversely, however, by sliding more easily, they areless effective for this reason in maintaining the sand.

So it is preferable only to use siliconised fibres when the fibres arelong, preferably for fibres longer than 3 cm.

Moreover, siliconised fibre does not retain water by capillary actionand the fact of using such a siliconised fibre would thus in principlereduce the water holding capacity.

And yet, quite the contrary, it has surprisingly emerged that usingwater-repellent fibres such as siliconised fibres is an extremelyeffective means of retaining water in the porous volume when thediameter of the drop of water on the water-repellent surface of thefibre is greater than the dimension of the passage between three grainsof sand less the diameter of the fibre, because the water, which entersthis cavity and recombines into a large drop due to the water-repellingproperty of the fibre, can no longer come out again by the passage takenby the fibre.

In practice, it has been found, surprisingly, that a water-repellentfibre, for example a siliconised fibre, in a sand whose D50 is less than500 μm, gives the substrate a hydric behaviour which is especiallyfavourable to the development of the turf.

Thus, a siliconised fibre in a sand of D50<500 μm and more particularlyin a sand of D50<350 μm, exhibits the double benefit of a lubricationenabling the fibre to be incorporated into the porous volume of saidsand, this incorporation being more difficult as the sand becomes finerand creating a completely new synergy between a porous volume ofhydrophilic granules and a fibre with a water-repellent surface to trapwater in the porous volume, this water being very easily usable by theroots of plants growing in the substrate.

Taking these factors into account, experience shows that an especiallysatisfactory result is obtained, both in mechanical terms and withrespect to the growth of the turf, taking account of the good waterholding capacity and good capillary action in a sand with a granulometryof between 200 μm and 400 μm and for a siliconised hollow polyesterfibre with a diameter of between 12 and 30 μm.

Experience shows that even better results are obtained with anon-siliconised fibre, but that it is more difficult to incorporate itwell and that effectiveness falls if it is not properly incorporated.For lengths of fibres of less than 80 mm, however, the choice ofnon-siliconised fibres is an attractive possibility if one has access toespecially effective means of incorporation.

It is also possible to use polyester fibre produced from industrialrecycling with cotton fabric.

It is possible to leave out the cotton, which plays no importantpositive mechanical role, still less a durable positive mechanical role,since it is biodegradable. But it has emerged, surprisingly, thatcotton, being extremely hydrophilic, delivers a very attractive reserveof water at the start of the life of the substrate, at the crucialmoment of the implantation of the turf by seeding or of implantation ofthe plants on a terrace or, again, for the transplantation of largetrees.

By the same token, it has surprisingly emerged that fibres, which arenot individualised, are less effective for the role initially planned,consisting of mechanically reinforcing the substrate. But thesenon-individualised fibres, which have appeared unexpectedly in theprocess of fabrication in the form of small unattractive clumps, haveturned out to be useful in giving a sort of structure to the substratewhich resembles the structuring of clods in a natural soil.

If the fibres are hydrophilic, but also, more unexpectedly, if they arenot hydrophilic but siliconised, the clumps have, surprisingly, turnedout to be highly effective in creating usable reserves of water in whichthe young rootlets primarily gather during seeding; and, what is more,it has unexpectedly emerged that these clumps effectively oppose thepenetration of a crampon for example, just as chignons of hair protectedwarriors by preventing a sabre, even if sharpened, from cutting theirnecks. It has also been realised, unexpectedly, that these clumps occupya large volume, which is liable to shrink in on itself and to regain itsvolume: finally, they constitute a sort of light, insulating, aeratedparticle, with a high reserve of water and resilient.

Too many, however, of these clumps, or surface elements, in addition tobeing especially unattractive on the surface, in particular render itextremely difficult to put the substrate in position and to level outthe surface; and, what is more, they may end up reducing the cohesion ofthe whole if continuous sliding surfaces can form from one clump toanother. In addition to having a mechanical effectiveness which isalmost nil in comparison with that of individualised fibres, thesefibres in clods, if they are more numerous than necessary, increase theprice of the substrate with no mechanical advantage.

That is why, according to this invention, the dosage of these surfaceelements must not represent more than 75% of the dosage (D_(F)+D_(Al))of all the inclusions of the third and fourth parts.

Surprisingly, it has been realised that the maximum dose of fibres whichcan be mixed into the substrate is very considerably greater if thesubstrate contains a predominant proportion of cork or of matter whichis resilient by comparison with sand; and, it has also been realised,even more surprisingly, that it is possible to constitute a substrate inwhich cork constitutes the essential part, sand being either absent, orvery much in the minority in terms of dosage by volume (for example adose of sand of under 30%): this cork-based substrate is, against allexpectations, for the same dosage of fibres, even more resistant toshearing than a substrate essentially composed of sand. So it has beenrealised, completely unexpectedly, that a substrate essentiallyconstituted of cork may allow a much higher dose of fibre, due to thefact that the fibre does not jam the machine which mixes the fibre andcork, by creating a shearing with the aid of the capacity for resilienceof the cork, which collapses in on itself, in order to pass throughwhere sand would be blocked in the process of fabrication.

In such a mixture, according to the invention, with the aid of grains ofcork which keep the fibres separate (which would otherwise agglomerateand become compacted), these constitute, in a mixture with cork, and forthe same reasons as this latter, a fully integrated constituent of thesubstrate, light, insulating, resilient, capable of capillary waterretention.

It has been found that, even more surprisingly, cork and fibre, partlyin the form of clumps and partly in the form of individualised strands,optionally with a little sand, constitute an extraordinary matrix, whichbehaves like a soil with respect to plants but which behaves, atmacroscopic scale, like a judo tatami, for example, i.e. like an elasticsolid.

This substrate can be moulded and compressed to its equilibriumthickness and it is possible to walk or jump on its edge withoutdestroying it: the edge may be compressed by several centimetres locallyunder the weight and immediately returns to its place.

The lower the portion of sand and the higher the proportion of resilientgrain, particularly of cork, the lower the density of the substrate andthe higher its coefficient of insulation.

For a substrate in which cork represents more than 50% by volume, themechanical characteristics of the substrate are hardly affected at allby frost. It has even been found that turf planted in a substrateaccording to this invention with a proportion of cork of over 75%remains resilient, while other soils are frozen and as hard as rock.

For a substrate of this type according to the invention, in which corkin the form of large granules represents over 20% and preferably over50%, and in which the sandy proportion has a D10 of over 200 μm,permeability is such that the substrate “drinks deep” and at the end ofthe worst precipitations holds only the water retained by capillaryaction.

The combination of water retained by capillary action and of thermalinsulation enables a reserve of water to be kept available for seedingfor a very long time and up to the surface.

A substrate according to this invention can be characterised, whateverits formulation, as follows:

firstly by the initial proportion by volume of each component of themixture, with the exception of the fibres, defined as the heaped volumeof the component before its incorporation divided by the sum of theheaped volumes of all the components before their incorporation (withthe exception of the fibres); and,

secondly by a gravimetric density of the fibre in the mixture defined asthe weight of the fibre divided by the sum of the heaped volumes of allthe components before their incorporation in the mixture, with theexception of the fibres.

Usually, when analysing soil, one considers in a mixture the proportionsby weight (as dry weight) of the different fractions, because the dryweight of the mixture is equal to the sum of the dry weights of theconstituents while the volume of a mixture is not necessarily equal tothe sum of the initial volumes of the constituents, because of theswelling or compaction of the mixture, as small particles can“disappear” in the porous volume of the large particles.

In practical terms, however, for the constituents other than fibre, tocharacterise the substrate, one uses the initial proportions by volumeas defined above, so that the sum of the initial proportions by volumeof all of the constituents does in fact make 100%.

The advantage within the frame of this invention of expressing thecomposition of the substrate as initial proportions by volume isthreefold:

firstly, the constituents used are selected to be non-swelling, whichindicates that the volume of the heap of each constituent remains thesame, whether the constituent is wet or dry, while the weight of theheap changes considerably as a function of the water content. The heapedvolume, and not the heaped weight, is thus proportional to the dryweight of the element concerned.

secondly the process of dosing the sand and the cork, as practised inthe frame of the invention, is done by the heaped volume and not byweight

finally, and above all, the densities of the constituents being verydifferent from each other, since for example sand is 20 times denserthan cork, a hypothetical initial proportion by volume of 75% of corkwould give a proportion by weight of 15% of cork while ¾ of the volumeis taken up by the cork and it is this occupation of space which meansthat the cork imposes its mechanical behaviour (density of the mixture,absorption capacity, resilience, thermal insulation, etc.) which is thusmore closely linked to the initial proportion by volume than to theproportion by weight.

In another version of the dosing process, the servo module for the startof the sand is controlled as a function of the variation of the weightof sand in a hopper and one could express the ratio between the volumeof cork and the weight of sand, but it is more meaningful to the personskilled in the art to consider the volume ratio between the cork and thesand; if the weight of the sand is known, it is sufficient to divide theweight by the density of sand even if this density is selectedarbitrarily or superficially, to convert the weight of the sand intovolume and arrive at the composition by volume with respect to thecomponents of sand and of cork.

With respect to the fibres, on the other hand, the initial volume of thefibres is not used, because the volume of the same quantity of fibresmay vary in a ratio of more than 10 as a function of the processing ofthese fibres, which may be heavily compressed and occupy a small volumeor on the other hand, be loosely packed and take up a huge volume. For agiven type of fibre, it is therefore the weight of fibre which is themost practical parameter for finding out the quantity of fibreincorporated.

A substrate according to this invention certainly has, as principalapplication, the realisation, optionally in situ, of sports surfaces,but also of terrace surfaces or a medium for the transplantation ofvegetables or for growing turf in strips.

The improvement in the characteristics of flexibility, of reducedsensitivity to compaction and thermal insulation is detectable once theproportion by volume of the resilient particles in the substrate is morethan 5% and the diameter of the fine fibres is less than 10% of thegranulometry of the hard particles of the first part. This improvementis naturally accentuated as the proportion of resilient particlesincreases. But the concomitant increase in the cost price and thedifficulty of conserving such good cohesion beyond 60% mean thatformulas with more than 60% by volume of resilient elements tend to bereserved for culture substrates for terracing; the formulas for sportsgrounds preferably contain less than 60% by volume of resilientelements.

Taking into account these elements, the substrate according to theinvention is available in several formulations which are very differentas a function of their applications.

Several elements allow the formulation to be identified as a function ofneeds.

The cost price rises very significantly with the increase in theproportion by volume PV of cork, which is a first element to limit theuse of cork for economic reasons. Moreover, although cork providesflexibility, depending on their intended use, it is necessary for fieldsto retain a certain performance and sufficient bounce: the field isfaster for racing or for the ball when it is harder; for example, it isnecessary to have sufficient bounce for the ball when playing footballor tennis: this is one reason to limit the use of cork on technicalgrounds.

Over a period of one year, experiments were carried out to improve theproduct and test the formulations.

To improve the product, different sources of fibres were sought and itwas realised that totally different results were obtained in terms ofmechanical behaviour with fibres which were only slightly different andmoreover with formulations which were exactly equivalent.

The thickness of the fibres is an important element, just as surfacecondition and length have proven to be decisive. If the fibres, all elsebeing equal, are too short in relation to the dimension of the grains,the stabilisation effect is very weak, sometimes even non-existent; themore the length increases, the more effective the fibres, for the samedosage of fibres, on condition they can be kept untangled, which is moreand more difficult when the length increases.

In order to improve the formulation and to incorporate fibres which wereas effective as possible, it was necessary to improve the defibrationsystem, which is intended to separate the fibres, to keep them separatedand to introduce them into the granular medium well separated, at thestrategic meeting point arranged in the mixing process.

Taking these improvements into account, it was possible to test numerousformulations with fibres which had been well defibred by installing themon a grid pattern and then testing the mechanical behaviour of differentformulations obtained, for different types of fibres, by varying theconcentration of fibres according to one axis of the grid pattern andthe concentration of cork according to the other axis.

In particular, tests were carried out with lengths of fibres of 40 mm,which proved effective but too short for good effectiveness, fibres of70 mm which proved to be very effective in obtaining a resilient andstable substrate, and 140 mm, which proved to be even more effective,especially with the most corky substrates.

For preference, it was found that the other elongated or surfaceinclusions which can be added to fibres to stabilise the substrate aremore effective if their largest dimension is at least 10 times greaterthan their smallest dimension and at least 10 times greater than themean granulometry of the particles constituting the skeleton of thesubstrate.

In the examples studied, it was necessary to choose a description of themixtures, taking into account what can be measured and the ratiosbetween the density of the cork and that of the sand. A process offormulation and automation of the fabrication of the mixtures has beenperfected, characterised in that there are three distribution deviceswhose flow can be regulated, a sand distributor, a cork distributor anda fibre distributor and the different flows are regulated in order toobtain a formulation equal to the proportion of distribution flows ofthe elementary components.

In this process, the flow of sand is characterised by the measuredweight of sand transiting per unit of time, while the flow of cork ischaracterised by the measured volume of cork passing per unit of timeand the flow of fibres is characterised by the weight of fibres passingper unit of time.

It was decided to characterise the granular medium by the proportion ofthe respective volumes of sand and of cork, but a difficulty arises forthe sand, whose volume depends on the state of compaction, and whoseweight is not known.

Taking into account the uncertainties of weight due to the waterattached to the sand, the weight of wet sand passing per unit of time ismeasured and in the fabrication and evaluation process an arbitraryvolume of sand, calculated on the basis of its weight, is taken intoaccount, deciding arbitrarily that the “arbitrary volume” of sand isthat which corresponds to the measured weight, for a selected arbitrarydensity, for example 1.4 kg/litre of sand; the proportion by volumebetween the sand and the cork is then characterised by considering thatthe proportion of sand is the ratio between the arbitrary volume of sandand the sum of the arbitrary volume of sand and of the measured volumeof cork, the sum of the proportions by volume of sand and of cork beingequal to 100%.

The dosage of the fibres is considered in grams per litre of mixture:one considers per unit of time the ratio between the weight of fibreadded and the arbitrary volume of the mixture equal to the sum of thearbitrary volume of sand and of the measured volume of cork in the sameunit of time.

What is referred to as the weight of fibre in relation to the volume ofthe mixture is in fact the ratio between the weight of fibres added andthe arbitrary volume of aggregates defined by the sum of the arbitraryvolume of sand and of measured volume of cork.

The perfected process is then characterised by the fact that firstly theflow of sand can be regulated and measured continuously by measuring thevariation in weight of a sand circulation system, for example bymounting this system on precision scales and by the fact that secondlythere is a computer program to automate these flows, enabling the flowsof cork and of fibre to be automatically linked to this measurement ofthe flow of sand as a function of the formulation required and also tocontinuously accelerate or to decelerate the flow of sand in order tokeep it at its planned flow rate, despite any flow irregularities linkedto irregularities of internal friction within the circuit.

Taking into account the progress already made, firstly in terms ofdefibrage, secondly of choice of fibres, and lastly of precision ofmixtures, it has been possible to test numerous formulationssystematically. Surprisingly, the results are very noticeably differentfrom the results originally obtained using less suitable fibres, lesswell defibred and mixed with less precision.

Surprisingly, the progress made in the choice of fibres and the methodof defibrage completely overturned the results previously obtained, asshown by the following examples of some tests.

Many tests were carried out on the different mixtures and relate to themechanical aspect, the agronomical and hydric aspect and to theadaptation of the product to different uses.

In particular, accelerometric tests enable the elasticity and the modesof dissipation of kinetic energy to be tested, while other tests allowthe cohesion and the angle of internal friction of the substrate to bemeasured.

The disadvantage of these tests is that they give measurements whichcharacterise the substrate, but without providing any threshold ofeffectiveness, whether this is a minimum or a maximum threshold.

We were able to define, in addition to scientific measurements ofcharacterisation, a very simple qualitative test for a minimum thresholdof effectiveness, and which seems pertinent to us because it is simpleto carry out, discriminating and reproducible, and correlated to therequired stability objective. This test consists, for a given substrate,of spreading it out over a low height and a small surface area,compacting it and then attempting to sink a spade into it: for a dosageof fibres of less than a certain dosage which defines the threshold ofeffectiveness revealed by this test, it is possible to sink the spade,while above this dosage, it becomes very difficult, then impossible todo so, as soon as this threshold of effectiveness is slightly exceeded;although completely dependant on the methodology of compacting and thehumidity or the way in which the spade is sunk, this test, realised insummary fashion by compacting with the feet, turned out to be completelyreproducible, even if it involves no great precision and it hastherefore been used in order to determine the minimum threshold offibres to incorporate into the different granular mixtures tested.

These tests revealed a sensitivity to fibres for low dosages but with aminimum dosage which increases with the quantity of fibres.

It was observed that it was preferable to have at least 0.5 g/l offibres to observe any effect of the fibres.

It is preferable to have at least 0.5 g/l of fibres and at least 1g/litre of the sum of fibres plus inclusions to obtain a visible resultwith a dose of cork greater than 5% and less than 60%.

It is preferable to have at least 1 g/l of fibres and at least 2 g/litreof the sum of fibres plus inclusions to obtain a visible result with adose of cork of more than 60%.

Preferably, maximum effectiveness is obtained for a substrate having adose of cork of less than 60% for a dosage of fibres plus elongated orsurface inclusions of between 2 g/litre and 80 g/litre.

Preferably, maximum effectiveness is obtained for a substrate having adose of cork of more than 60% for a dosage of fibres plus elongated orsurface inclusions of between 5 g/litre and 200 g/litre.

With respect to the maximum threshold of fibre utilisable in a mixture,it has not been possible to find an objective test for the minimumthreshold and it is necessary, in order to determine the preferredmaximum dose of non-intrinsic criteria which are, essentially, thepossibility and the benefit of putting more fibres into each granularmixture.

It has become evident that the more cork there is and the more it ispossible to integrate large quantities of fibres without “jamming” themixing machine, the more useful it is to add more of them to stabilisethe mixture.

The drawbacks of adding too much are:

firstly the difficulty of incorporating the fibre without jamming themixing machine

and the difficulty of keeping a mixture which is homogeneous andcompacts well,

then the increase in the cost of material

and the reduction in the rate of fabrication,

then the difficulty of spreading out the mixture and keeping it flat

and finally the increased difficulty of then avoiding the segregation ofsurplus and badly mixed fibres.

In general, however, tests have not revealed any obvious intrinsicmaterial drawback for too high a dosage of fibres, once they have beensuccessfully incorporated; by improving the production equipment, it hasbeen possible to mix very much larger doses than had previously beenimagined, without reaching a dosage which presents a behavioural defect,even if, when the dose of fibres increases too much:

the substrate becomes more and more difficult to put into position,

the substrate becomes more and more difficult to compact,

the substrate needs more and more water and mechanical force to becomecompacted,

the substrate becomes more and more desiccated,

the substrate becomes more and more subject to segregation as it dries,with fibres detaching over time on the surface of the substrate,

the substrate has degraded agronomic characteristics.

It is found that beyond a certain dosage the substrate no longerpresents itself as a granular matrix with fibres running around thegrains and separated from each other by these grains, but changescontinuously to become a fibrous matrix in which are incorporated theaggregates which are attached to the fibres by electrostatic forces orhydraulic cohesion and which continues to present itself as a culturesubstrate but with continuously altered density characteristics, and isless attractive for economic reasons.

In view of these new tests, therefore, it appears that there is no testfor a maximum threshold as there is a minimum threshold test, but thesimple finding is that there is a progressive reduction in the benefitof increasing the dosage of fibres, both economically and technically.Taking these new observations into account, no test has allowed thesetting of an intrinsic maximum threshold which must not be exceeded,even if the economic considerations or the difficulties of fabricationas things stand or again, the lack of any advantage observed inincreasing the dosage of fibres beyond a certain limit, allow apreferred maximum dosage to be set for the different tests carried out.

So it is not necessary to set a maximum dosage, even though it isdesirable, for preference, not to exceed a maximum dosage for use as asports surface, and particularly for dosages with a high sand content,because:

firstly, beyond a certain threshold, the soil becomes more and moredifficult to level when the dose of fibres increases,

and because, secondly, the price increases (price of the fibre andmixing time) without any significant advantage in terms of stabilisationhaving been observed in return.

For a dosage of cork of less than 60%, it is preferable to have a dosageof fibres of less than 80 g/litre.

Above 60% of cork and most particularly above 75% and up to 100% ofcork, it was realised, with new tests conducted, firstly, for use as aturf substrate for a car park or for roads suitable for motor vehiclesand secondly as a light substrate for terrace cultivation, that theseuses make a high dosage of fibres attractive, but with the intrinsicmaximum limits which became apparent.

In the case of terraces, the preferred dosages of cork lie between 60%and 95% (substrates of 100% cork were used, but the substrate has lesshold and there is a high segregation of fibres at above 90%).

When it was attempted to increase the dosage of fibres above 200 g/m³for dosages of cork of 95%, it was found that it was more useful to add5% of sand and to arrive at a substrate which was 90% cork and 10% sandthan to add 70 g/m³ of fibres because it is more or less equivalent interms of density of substrate compacted to the maximum, but with a sandysubstrate which compacts better and then holds in position, while theincrease in the weight of fibres increases the density of the substratebut at the same time gives a substrate which compacts less well andholds less well, at a much higher cost.

The preferred maximum dosage for a proportion of cork of over 60% is 300g/litre.

In the case of car parks or roadways, it emerged first of all that theincrease in the proportion of cork benefits friction and theanti-shearing effect but that a minimum density of sand is useful forthe action-reaction principle and the preferred dosage of cork liesbetween 40 and 70%.

It then emerged, in the same way, that the density of fibres must be ashigh as possible to create a maximum of links and the greatest possibleanti-shearing effect but that its increase comes up against the drawbackthat the surface no longer remains compact enough because water isnecessary to compact the volume, but that by drying out, there isrenewed proliferation and destabilisation.

It has also turned out to be preferable not to exceed an arbitrarydosage of 300 g/litre of aggregate.

For a football pitch, it is preferable to keep to a formulation which isvery low in cork at the low end of the range for economic reasons; butit is preferable to have between 5% and 20% of cork to improveflexibility; for top of the range pitches, it is preferable to havebetween 20 and 40% of cork, with a dosage of fibres of between 7 and 15%for pitches for normally intensive use and up to 20 g/l for heavily usedtraining pitches. For the ball to bounce adequately, there must not bemore than 60% of cork and to keep a fast pitch while improvingflexibility for players, it seems that 40% of cork is a good compromise.

For a golf green, the attraction of a substrate according to theinvention is to allow a dense surface which remains aerated, supportiveand hard, and suitably decompacted for growing the turf, with an easilyusable and sufficient reserve of water. To make the green faster, i.e.the speed of the ball on the green, which is generally desirable, theproportion of cork must be reduced, but the other aspect is to havegreens with a speed similar to other golf greens, so that the proportionof cork will preferably lie between 10% and 40%, depending on whetherthe aim is the performance of the green in question or homogeneity inrelation to other existing greens.

In the same way, for tennis, the quantity of cork has an influence overthe type of play; by increasing the proportion of cork, greater comfortis achieved, but the bounce is not so high and the speed of bounce islower, which is similar to the surface behaviour of that of a copiouslywatered clay, while a substrate according to the invention, with a lowproportion of cork, will make it possible to obtain a surface similar tothat of a turf made of grass on dry earth. Depending on the objectives,the preferred proportion of cork will be from 0 to 20% for a very fastsurface, between 20% and 40% for a soft and slower surface of the claytype and up to 60% for a very soft surface with slow play, suitable fortennis played for pleasure rather than for competition.

For a rugby pitch, flexibility and resistance are more important thanthe bounce of the ball and the best compromise lies, in technical terms,between 40 and 60% of cork with 15 to 20 g/litre of substrate or between20% and 40% of cork with 10 to 15 g/litre of fibres for a lower budgettraining pitch.

Football and rugby pitches may have a layer of substrate according tothe invention which is 10 to 15 cm thick or a layer of substrateaccording to the invention of 3 to 7 cm as surface, resting on asub-layer of sand of at least equal permeability.

At a time when there are concerns about both sustainable development andabout heating pitches so they can be used for sports in winter, corkpresents one great advantage by its isothermal nature: for this reason,it gives soil the ability to tolerate more intense cold without freezingand to remain warm enough for longer to allow turf to sprout or grow; inaddition to this isothermal nature, the resilient aspect of cork allowsthe soil to take up any expansion of water between 4° C. and 0° C. whenwater turns into ice: so the soil does not become hard and solid if thewater present in the substrate turns into ice, all the more so since thesubstrate according to the invention has very high permeability andretains only a small quantity of water by capillary action; most of thewater present in the porous volume being very rapidly evacuated bygravity if the substrate is placed, as it should be, on a surface withadequate drainage.

So substrates according to the invention enable the creation of a sportsfield which can be used in winter without heating, while other fieldsare as hard as rock and also, if heating of the substrate is installed,enables a higher temperature to be achieved for much less energyconsumption. Tests conducted have shown that, for the same heatingenergy distributed in the same way at the same time, the substrateaccording to the invention tested had a temperature 10° C. higher thanthat of the reference substrate.

As for horse racing tracks, there is a need for soils which are at thesame time much more resilient, because horses tend to run on wet grassin which their hooves sink by several centimetres, and very resistant inorder to avoid having to replace clods, as is currently the case, thiswork representing a very high cost. For this reason, the desirableformulations comprise a minimal proportion of cork, of between 40 and60%, and preferably an even higher proportion, between 60 and 80%, mostparticularly in the most sensitive areas such as approaches to jumps,the thicknesses of such a substrate being at least between 15 and 20 cm.

For show jumping arenas, these have to be resilient, but not too muchso, and above all must release energy: a proportion of between 10% and40% of cork would be suitable in technical terms.

Polo fields or trotting tracks must be even harder and the proportion ofcork may advantageously lie between 5% and 20%.

When the sports field or surface is constituted by juxtaposed cells,bounded by walls, these are filled with a substrate according to thepresent invention to a height at least equal to that of these walls.

When the level of the substrate exceeds the level of these walls by afew centimetres, the preferred substrate is a substrate comprising morethan 50% cork, because the lower density of the substrate and itsbehaviour as an elastic solid allows vertical edges going beyond thelevel of the walls and the playing surface to have good hold, whileguaranteeing the flexibility of the substrate.

1. Substrate intended for use as a culture medium, wherein the substratecontains: a first part, constituting the skeleton of the substrate andrepresenting more than 70% of the total volume of said substrate,composed of particles P_(>100 μm) with a granulometry greater than 100μm, all of said particles being constituted by hard particles P_(D>100)and/or resilient particles PR>₁₀₀, said resilient particles constitutinga proportion by volume PV of between 0% and 100% by volume of this firstpart; a second part of particulate elements P_(<100) with a granulometryof less than 100 μm, and constituting from 0 to 450 g/l of saidsubstrate; a third part, constituting from 0 to 200 g/l of saidsubstrate, composed of fine fibres with a length of between 3 mm and 100mm and a diameter of between 5 μm and 35 μm; a fourth part, constitutingfrom 0 to 200 g/l of said substrate, composed of other elongated and/orsurface inclusions, each of these elongated or surface inclusions havingat least one of their dimensions broadly greater than the granulometryof the particles of the first part, the sum of the dosage of the thirdpart and of the fourth part being greater than 0.5 g/l of saidsubstrate.
 2. Substrate according to claim 1, wherein all the particleswith a dimension greater than 180 μm and less than 100 μm represent lessthan 1000 g/l of substrate.
 3. Substrate according to claim 1, whereinfor a proportion by volume PV of resilient particles P_(R>100) of lessthan 5%, the sum of the dosage D_(F) of the fine fibres and of thedosage D_(Al) of all the other inclusions of the fourth part is greaterthan 0.5 g/litre of substrate and 20 g/litre of substrate.
 4. Substrateaccording to claim 1, wherein for a proportion by volume PV of resilientparticles P_(R>100) greater than 5% and the sum of the dosage D_(F) ofthe fine fibres and of the dosage D_(Al) of all the other inclusions ofthe fourth part is greater than 1 g/litre of substrate.
 5. Substrateaccording to claim 1, wherein for a proportion by volume PV of resilientparticles P_(R>100) of between 5% and 60%, the dosage D_(F) of the finefibres is greater than 1 g/litre of substrate, and the sum of the dosageD_(F) of the fine fibres and of the dosage D_(Al) of all the otherinclusions of the fourth part is less than 80 g/litre of substrate. 6.Substrate according to claim 1, wherein for a proportion by volume PV ofresilient particles P_(R>100) greater than 5% and 60%, the sum of thedosage D_(F) of the fine fibres and of the dosage D_(Al) of all theother inclusions of the fourth part is less than 300 g/litre ofsubstrate.
 7. Substrate according to claim 1, wherein for a proportionby volume PV of resilient particles P_(R>100) of less than 60%, the sumof the dosage D_(F) of the fine fibres and of the dosage D_(Al) of allthe other inclusions of the fourth part is between 2 g/litre ofsubstrate and 80 g/litre of substrate.
 8. Substrate according to claim1, wherein for a proportion by volume PV of resilient particlesP_(R>100) greater than 60%, the sum of the dosage D_(F) of the finefibres and of the dosage D_(Al) of all the other inclusions of thefourth part is between 5 g/litre of substrate and 200 g/litre ofsubstrate.
 9. Substrate according to claim 1, wherein the hard particlesof the first part are grains of silica sand.
 10. Substrate according toclaim 1, wherein the resilient particles of the first part are grains ofcork.
 11. Substrate according to claim 1, wherein the particulateelements of the second part are constituted of clay, of loam, of veryfine sand with a granulometry of less than 100 μm, of organic matter, offine porous elements such as zeolite powder, coral or diatomaceousearth.
 12. Substrate according to claim 1, wherein the particulateelements of the second part having a dimension of less than 20 μmrepresent less than 60 g/l of substrate and the particulate elements ofthe second part having a dimension of less than 100 μm represent lessthan 300 g/l of said substrate.
 13. Substrate according to claim 1,wherein the particulate elements of the second part having a dimensionof less than 80 μm represent less than 45 g/l of substrate. 14.Substrate according to claim 1, wherein at least 20% by weight of thefine fibres of the third part are hollow polyester fibres with adiameter of between 10 μm and 20 μm.
 15. Substrate according to claim 1,wherein at least 20% by weight of the fibres of the third part areencased in a lubricant water-repellent product.
 16. Substrate accordingto claim 15, wherein the lubricant water-repellent product is silicone.17. Substrate according to claim 1, wherein over 50% of the weight ofthe fine fibres of the third part is constituted by fine fibres whosediameter is less than 10% of the mean granulometry of the hard particlesof said substrate.
 18. Substrate according to claim 17, wherein theproportion by volume PV of the resilient particles P_(R>100) in thesubstrate is greater than 5% and less than 60% by weight, and that morethan 50% of the weight of the fine fibres of the third part isconstituted by fine fibres whose diameter is less than 10% of the meangranulometry of the hard particles.
 19. Substrate according to claim 1,wherein, firstly, more than 80% by weight of the hard particles presenta granulometry of between 200 μm and 400 μm, and that, secondly, thefine fibres of the third part are hollow polyester fibres, with adiameter of between 12 and 30 μm and siliconised on the surface. 20.Application of the substrate according to claim 1 to the creation,optionally in situ, of sports surfaces, of terrace surfaces, of a mediumfor the transplantation of vegetables or for growing turf in strips. 21.(canceled)